[6600gt]

Any laptop with a dedicated graphics card by nVidia or ATI with 128mb+ dedicated graphics memory can handle AutoCAD or Inventor.

So basically, look for a laptop with a nice screen, 2GB of Ram, 100GB+ HD, Dedicated Graphics(important), and a dual core processor (either AMD or Intel).

If the laptop has dedicated graphics (most of AMD solutions do), a $600-$700 laptop will more than enough for most of your needs(but you might get the 2GB RAM in the price range). 3dsMax type animations will easily require 2GB or more RAM.

All the horsepower in the world won't help you if you don't optimize it. My desktop with an AMD Sempron can do all the things you require plus more. The only thing it has that would be somewhat expensive for laptop is a 6600GT graphics card. Though the sempron is somewhat limiting for gaming(BF2142), it can handle Inventor just fine. It lacks the raw power but optimizations keep it running smooth.